reserved for future use

Formatter for printing and parsing date-time objects.

This class provides the main application entry point for printing and parsing
and provides common implementations of DateTimeFormatter:

Using predefined constants, such as ISO_LOCAL_DATE
Using pattern letters, such as uuuu-MMM-dd
Using localized styles, such as long or medium


More complex formatters are provided by
DateTimeFormatterBuilder.


The main date-time classes provide two methods - one for formatting,
format(DateTimeFormatter formatter), and one for parsing,
parse(CharSequence text, DateTimeFormatter formatter).
For example:


 LocalDate date = LocalDate.now();
 String text = date.format(formatter);
 LocalDate parsedDate = LocalDate.parse(text, formatter);

In addition to the format, formatters can be created with desired Locale,
Chronology, ZoneId, and DecimalStyle.

The withLocale method returns a new formatter that
overrides the locale. The locale affects some aspects of formatting and
parsing. For example, the ofLocalizedDate provides a
formatter that uses the locale specific date format.

The withChronology method returns a new formatter
that overrides the chronology. If overridden, the date-time value is
converted to the chronology before formatting. During parsing the date-time
value is converted to the chronology before it is returned.

The withZone method returns a new formatter that overrides
the zone. If overridden, the date-time value is converted to a ZonedDateTime
with the requested ZoneId before formatting. During parsing the ZoneId is
applied before the value is returned.

The withDecimalStyle method returns a new formatter that
overrides the DecimalStyle. The DecimalStyle symbols are used for
formatting and parsing.

Some applications may need to use the older java.text.Format
class for formatting. The toFormat() method returns an
implementation of java.text.Format.

Predefined Formatters



Formatter
Description
Example




ofLocalizedDate(dateStyle)
 Formatter with date style from the locale
 '2011-12-03'


 ofLocalizedTime(timeStyle)
 Formatter with time style from the locale
 '10:15:30'


 ofLocalizedDateTime(dateTimeStyle)
 Formatter with a style for date and time from the locale
 '3 Jun 2008 11:05:30'


 ofLocalizedDateTime(dateStyle,timeStyle)

 Formatter with date and time styles from the locale
 '3 Jun 2008 11:05'


 BASIC_ISO_DATE
Basic ISO date  '20111203'


 ISO_LOCAL_DATE
 ISO Local Date
'2011-12-03'


 ISO_OFFSET_DATE
 ISO Date with offset
'2011-12-03+01:00'


 ISO_DATE
 ISO Date with or without offset
 '2011-12-03+01:00'; '2011-12-03'


 ISO_LOCAL_TIME
 Time without offset
'10:15:30'


 ISO_OFFSET_TIME
 Time with offset
'10:15:30+01:00'


 ISO_TIME
 Time with or without offset
'10:15:30+01:00'; '10:15:30'


 ISO_LOCAL_DATE_TIME
 ISO Local Date and Time
'2011-12-03T10:15:30'


 ISO_OFFSET_DATE_TIME
 Date Time with Offset
2011-12-03T10:15:30+01:00'


 ISO_ZONED_DATE_TIME
 Zoned Date Time
'2011-12-03T10:15:30+01:00[Europe/Paris]'


 ISO_DATE_TIME
 Date and time with ZoneId
'2011-12-03T10:15:30+01:00[Europe/Paris]'


 ISO_ORDINAL_DATE
 Year and day of year
'2012-337'


 ISO_WEEK_DATE
 Year and Week
2012-W48-6'

 ISO_INSTANT
 Date and Time of an Instant
'2011-12-03T10:15:30Z'


 RFC_1123_DATE_TIME
 RFC 1123 / RFC 822
'Tue, 3 Jun 2008 11:05:30 GMT'




Patterns for Formatting and Parsing
Patterns are based on a simple sequence of letters and symbols.
A pattern is used to create a Formatter using the
ofPattern(String) and ofPattern(String, Locale) methods.
For example,
"d MMM uuuu" will format 2011-12-03 as '3 Dec 2011'.
A formatter created from a pattern can be used as many times as necessary,
it is immutable and is thread-safe.

For example:


 LocalDate date = LocalDate.now();
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy MM dd");
 String text = date.format(formatter);
 LocalDate parsedDate = LocalDate.parse(text, formatter);

All letters 'A' to 'Z' and 'a' to 'z' are reserved as pattern letters. The
following pattern letters are defined:


 Symbol  Meaning                     Presentation      Examples
 ------  -------                     ------------      -------
  G       era                         text              AD; Anno Domini; A
  u       year                        year              2004; 04
  y       year-of-era                 year              2004; 04
  D       day-of-year                 number            189
  M/L     month-of-year               number/text       7; 07; Jul; July; J
  d       day-of-month                number            10

  Q/q     quarter-of-year             number/text       3; 03; Q3; 3rd quarter
  Y       week-based-year             year              1996; 96
  w       week-of-week-based-year     number            27
  W       week-of-month               number            4
  E       day-of-week                 text              Tue; Tuesday; T
  e/c     localized day-of-week       number/text       2; 02; Tue; Tuesday; T
  F       week-of-month               number            3

  a       am-pm-of-day                text              PM
  h       clock-hour-of-am-pm (1-12)  number            12
  K       hour-of-am-pm (0-11)        number            0
  k       clock-hour-of-am-pm (1-24)  number            0

  H       hour-of-day (0-23)          number            0
  m       minute-of-hour              number            30
  s       second-of-minute            number            55
  S       fraction-of-second          fraction          978
  A       milli-of-day                number            1234
  n       nano-of-second              number            987654321
  N       nano-of-day                 number            1234000000

  V       time-zone ID                zone-id           America/Los_Angeles; Z; -08:30
  z       time-zone name              zone-name         Pacific Standard Time; PST
  O       localized zone-offset       offset-O          GMT+8; GMT+08:00; UTC-08:00;
  X       zone-offset 'Z' for zero    offset-X          Z; -08; -0830; -08:30; -083015; -08:30:15;
  x       zone-offset                 offset-x          0000; -08; -0830; -08:30; -083015; -08:30:15;
  Z       zone-offset                 offset-Z          0000; -0800; -08:00;

  p       pad next                    pad modifier      1

  '       escape for text             delimiter
  ''      single quote                literal           '
  [       optional section start
  ]       optional section end
  #       reserved for future use
  {       reserved for future use
  }       reserved for future use

The count of pattern letters determines the format.

Text: The text style is determined based on the number of pattern
letters used. Less than 4 pattern letters will use the
short form. Exactly 4 pattern letters will use the
full form. Exactly 5 pattern letters will use the
narrow form.
Pattern letters 'L', 'c', and 'q' specify the stand-alone form of the text styles.

Number: If the count of letters is one, then the value is output using
the minimum number of digits and without padding. Otherwise, the count of digits
is used as the width of the output field, with the value zero-padded as necessary.
The following pattern letters have constraints on the count of letters.
Only one letter of 'c' and 'F' can be specified.
Up to two letters of 'd', 'H', 'h', 'K', 'k', 'm', and 's' can be specified.
Up to three letters of 'D' can be specified.

Number/Text: If the count of pattern letters is 3 or greater, use the
Text rules above. Otherwise use the Number rules above.

Fraction: Outputs the nano-of-second field as a fraction-of-second.
The nano-of-second value has nine digits, thus the count of pattern letters
is from 1 to 9. If it is less than 9, then the nano-of-second value is
truncated, with only the most significant digits being output.

Year: The count of letters determines the minimum field width below
which padding is used. If the count of letters is two, then a
reduced two digit form is
used. For printing, this outputs the rightmost two digits. For parsing, this
will parse using the base value of 2000, resulting in a year within the range
2000 to 2099 inclusive. If the count of letters is less than four (but not
two), then the sign is only output for negative years as per
SignStyle.NORMAL. Otherwise, the sign is output if the pad width is
exceeded, as per SignStyle.EXCEEDS_PAD.

ZoneId: This outputs the time-zone ID, such as 'Europe/Paris'. If the
count of letters is two, then the time-zone ID is output. Any other count of
letters throws IllegalArgumentException.

Zone names: This outputs the display name of the time-zone ID. If the
count of letters is one, two or three, then the short name is output. If the
count of letters is four, then the full name is output. Five or more letters
throws IllegalArgumentException.

Offset X and x: This formats the offset based on the number of pattern
letters. One letter outputs just the hour, such as '+01', unless the minute
is non-zero in which case the minute is also output, such as '+0130'. Two
letters outputs the hour and minute, without a colon, such as '+0130'. Three
letters outputs the hour and minute, with a colon, such as '+01:30'. Four
letters outputs the hour and minute and optional second, without a colon,
such as '+013015'. Five letters outputs the hour and minute and optional
second, with a colon, such as '+01:30:15'. Six or more letters throws
IllegalArgumentException. Pattern letter 'X' (upper case) will output
'Z' when the offset to be output would be zero, whereas pattern letter 'x'
(lower case) will output '+00', '+0000', or '+00:00'.

Offset O: This formats the localized offset based on the number of
pattern letters. One letter outputs the short
form of the localized offset, which is localized offset text, such as 'GMT',
with hour without leading zero, optional 2-digit minute and second if
non-zero, and colon, for example 'GMT+8'. Four letters outputs the
full form, which is localized offset text,
such as 'GMT, with 2-digit hour and minute field, optional second field
if non-zero, and colon, for example 'GMT+08:00'. Any other count of letters
throws IllegalArgumentException.

Offset Z: This formats the offset based on the number of pattern
letters. One, two or three letters outputs the hour and minute, without a
colon, such as '+0130'. The output will be '+0000' when the offset is zero.
Four letters outputs the full form of localized
offset, equivalent to four letters of Offset-O. The output will be the
corresponding localized offset text if the offset is zero. Five
letters outputs the hour, minute, with optional second if non-zero, with
colon. It outputs 'Z' if the offset is zero.
Six or more letters throws IllegalArgumentException.

Optional section: The optional section markers work exactly like
calling DateTimeFormatterBuilder.optionalStart() and
DateTimeFormatterBuilder.optionalEnd().

Pad modifier: Modifies the pattern that immediately follows to be
padded with spaces. The pad width is determined by the number of pattern
letters. This is the same as calling
DateTimeFormatterBuilder.padNext(int).

For example, 'ppH' outputs the hour-of-day padded on the left with spaces to
a width of 2.

Any unrecognized letter is an error. Any non-letter character, other than
'[', ']', '{', '}', '#' and the single quote will be output directly.
Despite this, it is recommended to use single quotes around all characters
that you want to output directly to ensure that future changes do not break
your application.

Resolving
Parsing is implemented as a two-phase operation.
First, the text is parsed using the layout defined by the formatter, producing
a Map of field to value, a ZoneId and a Chronology.
Second, the parsed data is resolved, by validating, combining and
simplifying the various fields into more useful ones.

Five parsing methods are supplied by this class.
Four of these perform both the parse and resolve phases.
The fifth method, parseUnresolved(CharSequence, ParsePosition),
only performs the first phase, leaving the result unresolved.
As such, it is essentially a low-level operation.

The resolve phase is controlled by two parameters, set on this class.

The ResolverStyle is an enum that offers three different approaches,
strict, smart and lenient. The smart option is the default.
It can be set using withResolverStyle(ResolverStyle).

The withResolverFields(TemporalField...) parameter allows the
set of fields that will be resolved to be filtered before resolving starts.
For example, if the formatter has parsed a year, month, day-of-month
and day-of-year, then there are two approaches to resolve a date:
(year  month  day-of-month) and (year  day-of-year).
The resolver fields allows one of the two approaches to be selected.
If no resolver fields are set then both approaches must result in the same date.

Resolving separate fields to form a complete date and time is a complex
process with behaviour distributed across a number of classes.
It follows these steps:

The chronology is determined.
The chronology of the result is either the chronology that was parsed,
or if no chronology was parsed, it is the chronology set on this class,
or if that is null, it is IsoChronology.
The ChronoField date fields are resolved.
This is achieved using Chronology.resolveDate(Map, ResolverStyle).
Documentation about field resolution is located in the implementation
of Chronology.
The ChronoField time fields are resolved.
This is documented on ChronoField and is the same for all chronologies.
Any fields that are not ChronoField are processed.
This is achieved using TemporalField.resolve(Map, TemporalAccessor, ResolverStyle).
Documentation about field resolution is located in the implementation
of TemporalField.
The ChronoField date and time fields are re-resolved.
This allows fields in step four to produce ChronoField values
and have them be processed into dates and times.
A LocalTime is formed if there is at least an hour-of-day available.
This involves providing default values for minute, second and fraction of second.
Any remaining unresolved fields are cross-checked against any
date and/or time that was resolved. Thus, an earlier stage would resolve
(year  month  day-of-month) to a date, and this stage would check that
day-of-week was valid for the date.
If an excess number of days
was parsed then it is added to the date if a date is available.

Builder to create date-time formatters.

This allows a DateTimeFormatter to be created.
All date-time formatters are created ultimately using this builder.

The basic elements of date-time can all be added:

Value - a numeric value
Fraction - a fractional value including the decimal place. Always use this when
outputting fractions to ensure that the fraction is parsed correctly
Text - the textual equivalent for the value
OffsetId/Offset - the java.time.zone offset
ZoneId - the java.time.time-zone id
ZoneText - the name of the time-zone
ChronologyId - the java.time.chrono.chronology id
ChronologyText - the name of the chronology
Literal - a text literal
Nested and Optional - formats can be nested or made optional

In addition, any of the elements may be decorated by padding, either with spaces or any other character.

Finally, a shorthand pattern, mostly compatible with java.text.SimpleDateFormat SimpleDateFormat
can be used, see appendPattern(String).
In practice, this simply parses the pattern and calls other methods on the builder.

An exception thrown when an error occurs during parsing.

This exception includes the text being parsed and the error index.

Localized decimal style used in date and time formatting.

A significant part of dealing with dates and times is the localization.
This class acts as a central point for accessing the information.